r 2025 CX-90 (built in December 2024) hasn't experienced any battery problems. Although I'm sorry to hear that yours failed, the battery guarantee should still cover quite a bit of time. According to service bulletin SA-018/25, Mazda will cover the hybrid batteries for 8 years or 80,000 miles on the MHEV.
Even without the extra coverage specified in the advisory, it would have been covered beyond the drivetrain guarantee for 7 years / 70,000 miles if you reside in one of the approximately 20 states that follow California emissions requirements. See the warranty handbook for further information.
On the underside of the engine, you won't find any parts that need servicing. For example, the timing chain is one of those mechanical components that is supposed to endure the lifetime of the car, but if it were to fail, it would necessitate costly engine-out repairs. When it comes to other Skyactiv engines, the timing chains and guides from Mazda usually last 200,000 miles or more with regular oil changes.
In order to change the timing chain on many cars, you have to take the engine cover off. Not exclusive to Mazda inline sixes, and it seems a bit hypocritical, if not exaggerated, to make a huge fuss about it like a certain famous YouTuber did.